Abrasive powder of fused alumina containing vanadium tetroxide

ABSTRACT

Excellent abrasive materials are provided by incorporating between about 0.1 and 7.5 percent, preferably 0.25 and 5.0 percent, and optimally about 1.5 percent by weight of vanadium tetroxide into a material high in alumina content, such as bauxite, corundum and relatively pure alumina. The vanadium tetroxide is fused per se in the alumina-containing material under non-reducing conditions or, preferably introduced as vanadium pentoxide with a stoichiometric amount of a reducing agent, such as aluminum metal, carbon, etc., to reduce the vanadium pentoxide to vanadium tetroxide. The fusion of the vanadium tetroxide in the alumina is accomplished in an electric furnace whereby the electric current is conducted through a layer of molten alumina at the bottom of the furnace with the liquid layer being covered with a substantial layer of a mixture of powdered solid alumina and the vanadium tetroxide-providing source.

United States Patent 1 1 Schleifer et al.

1451' Feb. 19, 1974 i 1 ABRASIVE POWDER OF FUSED ALUMINA CONTAININGVANADIUM TETROXIDE [75] Inventors: Ronald II. Schleifer, Churchville;

James E. Price, Abington, both of Pa.; Henry J. Bowden, Arvida, Quebec,Canada [73] Assignee: Wallace-Murray Corporation, New

York, NY.

22 Filed: Sept. 28, 1971 21 Appl. No.: 184,629 1 [52] US. Cl 51/309,51/298, 51/308, 106/65 [51] Int. Cl C04b 31/16, C09c H68 [58] Field ofSearch 51/309, 308, 307; 106/65 [56] References Cited UNITED STATESPATENTS 2,360,841 10/1944 Baumann et a1 5l/309.1

2,369,709 2/1945 Baumann et a1 51/309.1

2,418,496 4/1947 Baumann et al.. 51/309 2,961,296 11/1960 Fenerty 51/3093,615,307 10/1971 Jones 51/309 Primary Examiner-Donald J. ArnoldAttorney, Agent, or Firm-Louis F. Reed [5 7] ABSTRACT Excellent abrasivematerials are provided by incorporating between about 0.1 and 7.5percent, preferably 0.25 and 5.0 percent, and optimally about 1.5percent by weight of vanadium tetroxide into a material high in aluminacontent, such as bauxite, corundum and relatively pure alumina, Thevanadium tetroxide is fused per se in the alumina-containing materialunder non-reducing conditions or, preferably introduced as vanadiumpentoxide with a stoichiometric amount of a reducing agent, such asaluminum metal, carbon, etc., to reduce the vanadium pentoxide tovanadium tetroxide.

The fusion of the vanadium tetroxide in the alumina is accomplished inan electric furnace whereby the electric current is conducted through alayer of molten alumina at the bottom of the furnace with the liquidlayer being covered with a substantial layer of a mixture of powderedsolid alumina and the vanadium tetroxide-providing source.

12 Claims, N0 Drawings ABRASIVE POWDER or FUSED ALUMINA CONTAINING,VANADIUM TETROXIDE BACKGROUND OF THE INVENTION The present inventionrelates to excellent and improved alumina refractories and abrasives andabrasive articles produced therefrom. The inventionalso relates to anovel process for producing the abrasive powders of the invention.

Abrasive materials based on bauxite or othermaterials high in aluminahave long been utilized as commercial abrasives. The prior art disclosesthe production of abrasive materials from alumina or bauxite bypreparation under reducing conditions in an electric furnace. Inaccordance with one known product a solid solution is provided ofchromium sesquioxide in alumina and upon being crushed provides areddish abrasive which has been a commercial abrasive of choice for sometime.

There is disclosed in British patent 574,843 an abrasive materialcomprising alumina containing from 0.25 to 20 percent of chromiumsesquioxide or vanadium sesquioxide in solid solution in the grains.Although the British patent suggests a bright future for the abrasivematerial of the patent, the vanadium sesquioxidecontaining aluminaproduct of the patent has never been produced commercially so far as isknown.

Baumann et al. US. Pat. No. 2,418,496 deals with subject matter somewhatrelated to the British patent, but it is more concerned with a sinteredalumina grain containing in its exterior surface small amounts ofvanadium sesquioxide, chromium sesquioxide and certain oxides of othermetals. These materials are described as being case-treated aluminaparticles. These vanadium sesquioxide case-treated products have alsonever been produced commercially so far as is known. The shortcomings ofvanadium sesquioxide in alumina abrax s. is s s thi ra snt gq qmnsl nwherein it is stated that none of the oxides other than chromiumsesquioxide forms a continuous solid solution with alumina. I

Baumann et al. US. Pat. No. 2,369,709 refers to sintered products ofalumina with titanium oxide and chromium sesquioxide, manganesesesquioxide, vanadium sesquioxide, or vanadium pentoxide as the sourceof vanadium sesquioxide.

Rosenberg et al. US. Pat. No. 2,768,887 describes a process forproducing alumina abrasives containing solid solutions of small amountsof reduced metal oxides by an electric furnace. In the process of thatpatent an electric furnace is employed to fuse the mixture to provide athin liquid layer of molten substance which is supported on the surfaceof solidified material. This is just the opposite of the processemployed in the present invention whereby the initial molten pool ofmaterial is fed alumina powder plus additive vanadium oxide until theentire furnace charge is liquified. The surface of the liquified chargeis kept covered with powdered mix throughout the furnacing operation.

It is an object of the present invention to provide alumina basedmaterials having superior abrasive characteristics.

It is also an object of the present invention to provide a vanadiumtetroxide-containing alumina grain which provides an abrasion materialwhich can be readily fabricated into abrasive articles, such as grindingwheels and the like.

It is a further object of the present invention to provide a novelprocess for providing the vanadium tetroxide-containing aluminaabrasives of the invention.

Other objects will become apparent to those skilled in the art from thepresent description.

SUMMARY OF THE INVENTION It has been discovered that excellent abrasivematerials are provided by fusing throughout a material high in alumina,such as bauxite, corundum or pure alpha alumina, between about 0.1 and7.5 percent by weight of vanadium tetroxide, preferably 0.25 to 5.0percent vanadium tetroxide, and optimally 1.5 percent, into the aluminacontaining material by fusion. The compositions of the invention provideexcellent abrasive characteristics which make them suitable for acommercially desirable abrasive material or abrasive articles producedfrom it.

The present invention comprises an excellent abrasive material formedfrom materials high in alumina,

such as calcined alumina, bauxite having more than percent alumina orcorundum, consisting essentially of alpha alumina containing in solidsolution substantially uniformly throughout the material between about0.1 and 7.5 percent; preferably from 0.25 to 5.0 percent, and optimally1.5 percent by weight vanadium tetroxide based on weight of alumina inthe material. These products are produced by incorporating a desiredamount of vanadium tetroxide per se in the alumina and fusing it undernon-reducing conditions or by incorporating the corresponding amount ofvanadium pentoxide into the alumina and fusing it with a stoichiometricamount of aluminum, carbon, or other reducing agent, to produce thedesired amount of vanadium tetroxide when fused with the alumina in anelectric furnace in accordance with the process of the presentinvention.

The introduction of the vanadium tetroxide in solid solution isextraordinarily effective in increasing the hardness and toughness ofthe alumina.

In accordance with the process of the present invention the fusion takesplace at a temperature of between about 3400 and 4000F. in an electricfurnace wherein the molten portion of a mixture of alumina and vanadiumtetroxide or vanadium tetroxide-providing material is covered by thesolid powdered unmolten mixture of the same components of a thicknesssufficient to prevent oxidation and heat loss. When the entire chargehas been fused it is allowed to cool in the furnace or is poured intoseparate cooling receptacles. In either case the cooled solid solutionis crushed to the desired abrasive grit sizes.

The abrasive materials of the invention are characterized by a uniquegreenish color. With contents of about 1.25 percent vanadium tetroxideand above the color is deep green and at lower contents the color islight green.

From the abrasive materials of the invention, abrasive articles, such asgrinding wheels and the like, may be produced having excellent abrasiveproperties, although the abrasive powders have excellent abrasiveproperties and can be used in powdered form. For example, grindingwheels of the abrasive materials of the invention have a life of 8 hourscompared to only 2 hours of otherwise identical wheels employingordinary white alumina, when used under identical circumstances. Also,the grinding wheels of the invention reduce the time of grinding anidentical part or piece of metal, for example from 60 to 34 seconds.

DETAILED DESCRIPTION OF THE INVENTION In order to disclose more clearlythe nature of the present invention, the following examples illustratingthe invention are given. It should be understood, however, that this isdone solely by way of example and is intended neither to delineate thescope of the invention nor limit the ambit of the appended claims. Inthe examples which follow, and throughout the specification, thequantities of material are expressed in terms of parts or percentages byweight, unless otherwise specified.

EXAMPLE 1 To about 4000 pounds of finely divided Bayerprocess alumina ofhigh purity there was added 1.35 percent by weight of substantially purevanadium pentoxide and 6.48 pounds of aluminum metal (the stoichiometricamount of aluminum metal to reduce all of the vanadium pentoxide tovanadium tetroxide in accordance with the equation-3V O 2A1 A1 3V O,)and the composition was mixed thoroughly. It was then placed in aHiggins-type electric furnace and fused at a temperature of about 3800F.for 12 hours, using three-phase power at 115 volts with approximately1000 amperes on each electrode, or a total of 200 KVA. In accordancewith the preferred process of the invention, at substantially all timesthe melt was covered by a layer of powdered unfused mixture. Aftercooling in the furnace the mass was crushed by rolls to produce abrasiveparticles which were uniformly deep green in color.

EXAMPLE 2 To about 20,000 pounds of finely divided high purity aluminathere was added 1.35% by weight of substantially pure vanadium pentoxideand 21.6 pounds of petroleum coke (the stoichiometric amount of carbonto reduce all of the vanadium pentoxide to vanadium tetroxide inaccordance with the equation-V 0 C C0 V 0 and the composition was mixedthoroughly. It was then placed in a furnace and heated to a temperatureof about 3800F. for 60 hours. In accordance with the preferred processof the invention, at substantially all times the melt was covered by alayer of powdered unfused mixture. After cooling in the furnace, themass was crushed by rolls to produce abrasive particles which wereuniformly deep green in color.

EXAMPLE 3 To about 4000 pounds of finely divided alumina there was added0.75 percent by weight of substantially pure vanadium pentoxide and 3.60parts by weight of aluminum metal powder (the stoichiometric amount ofaluminum to reduce all of the vanadium pentoxide to vanadium tetroxide)and thecomposition was mixed thoroughly. It was then placed in a furnaceand heated to a temperature of about 3800F for 12 hours. In accordancewith the preferred process of the invention, at substantially all timesthe melt was.covered by a layer of powdered unfused mixture. Aftercooling in the furnace, the mass was crushed by rolls to produceabrasive particles which were uniformly bluish-green in color.

In the foregoing examples the vanadium pentoxide and reducing agent maybe replaced by an equivalent amount of vanadium tetroxide per se.

The green alumina abrasive particles from the fore going examples issuitable for producing abrasive articles such as grinding wheels and thelike in the usual manner with which the art is familiar.

EXAMPLE 4 In accordance with one method of producing grinding wheels,employing vitrification, a mixture of the particles of any one ofExamples 1-3 and 8 percent by weight of siliceous vitreous bonding agentwere pressed into the desired shape, such as that of a grinding wheel,and fixed at a temperature of 1750 F. for 16 hours. The grinding wheelwhich was then formed had a green color.

EXAMPLE 5 In accordance with another vitrification method of formingabrasive articlesv from the abrasive powder of the invention, the powderfrom any of the Examples l-3 was molded into the form of grinding wheeland fixed in air at 2250 F. for 128 hours, after which the color of thearticle was olive, which reflected a color transition which takes placeat highly elevated temperatures.

EXAMPLE 6 Employing 10 percent by weight ofa phenolic bonding resin, agrinding wheel was fabricated by molding an abrasive powder inaccordance with any of Examples 1-3 after which the wheel was cured at atemperature of 350 F. for 48 hours. The resulting grinding wheelretained the green color which is characteristic of the abrasive powdersof the present invention.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

What is claimed is:

1. An abrasive powder material consisting essentially of fused aluminacontaining between about 0.1 and 7.5 percent by weight of vanadiumtetroxide in solid solution.

2. An abrasive powder material in accordance with claim 1 wherein theamount of vanadium tetroxide is between about 0.25 and 5.0 percent byweight.

3. An abrasive material in accordance with claim 1 wherein the amount ofvanadium tetroxide is about 1.5 percent by weight.

4. An abrasive article of bonded abrasive grains, said grains beingconsisting essentially of fused alumina containing between about 0.1 and7.5 percent by weight of vanadium tetroxide in solid solution.

5. An abrasive article in accordance with claim 4 wherein the amount ofvanadium tetroxide is between about 0.25 and 5.0 percent by weight.

6. An abrasive article in accordance with claim 4 wherein the amount ofvanadium tetroxide is about 1.5 percent by weight.

7. A grinding wheel of bonded abrasive grains, said grains consistingessentially of alumina containing between about 0.1 and 7.5 percent byweight of vanadium tetroxide in solid solution.

8. A grinding wheel in accordance with claim 7 wherein the amount ofvanadium tetroxide is between about 0.25 and 5.0 percent by weight.

9. A grinding wheel in accordance with claim 7 wherein the amount ofvanadium tetroxide is about 1.5 percent by weight.

10. A process for producing an abrasive material comprising fusing amixture of alumina and between about 0.1 and 7.5 percent by weight ofvanadium pentoxide and a stoichiometric quantity of a reducing agent toreduce substantially all of the vanadian pentoxide to vanadiumtetroxide, providing a cover layer of unmolten mixture of alumina andvanadium pentoxide over the fused mixture substantially throughout thefusion process, cooling the resulting fused mixture of alumina andvanadium tetroxide to a solid, and crushing to particles of desiredsize.

11. A process according to claim 10 wherein the reducing agent is amember of the class consisting of aluminum metal and carbon.

12. A process for producing an abrasive material comprising fusing undernon-reducing conditions a mixture of alumina and between about 0.1 and7.5 percent by weight of vanadium tetroxide, providing a cover layer ofunmolten mixture over the fused mixture substantially throughout thefusion process, cooling the fused mixture to a solid, and crushing toparticles of desired size.

2. An abrasive powder material in accordance with claim 1 wherein theamount of vanadium tetroxide is between about 0.25 and 5.0 percent byweight.
 3. An abrasive material in accordance with claim 1 wherein theamount of vanadium tetroxide is about 1.5 percent by weight.
 4. Anabrasive article of bonded abrasive grains, said grains being consistingessentially of fused alumina containing between about 0.1 and 7.5percent by weight of vanadium tetroxide in solid solution.
 5. Anabrasive article in accordance with claim 4 wherein the amount ofvanadium tetroxide is between about 0.25 and 5.0 percent by weight. 6.An abrasive article in accordance with claim 4 wherein the amount ofvanadium tetroxide is about 1.5 percent by weight.
 7. A grinding wheelof bonded abrasive grains, said grains consisting essentially of aluminacontaining between about 0.1 and 7.5 percent by weight of vanadiumtetroxide in solid solution.
 8. A grinding wheel in accordance withclaim 7 wherein the amount of vanadium tetroxide is between about 0.25and 5.0 percent by weight.
 9. A grinding wheel in accordance with claim7 wherein the amount of vanadium tetroxide is about 1.5 percent byweight.
 10. A process for producing an abrasive material comprisingfusing a mixture of alumina and between about 0.1 and 7.5 percent byweight of vanadium pentoxide and a stoichiometric quantity of a reducingagent to reduce substantially all of the vanadian pentoxide to vanadiumtetroxide, providing a cover layer of unmolten mixture of alumina andvanadium pentoxide over the fused mixture substantially throughout thefusion process, cooling the resulting fused mixture of alumina andvanadium tetroxide to a solid, and crushing to particles of desiredsize.
 11. A process according to claim 10 wherein the reducing agent isa member of the class consisting of aluminum metal and carbon.
 12. Aprocess for producing an abrasive material comprising fusing undernon-reducing conditions a mixture of alumina and between about 0.1 and7.5 percent by weight of vanadium tetroxide, providing a cover layer ofunmolten mixture over the fused mixture sUbstantially throughout thefusion process, cooling the fused mixture to a solid, and crushing toparticles of desired size.